Systems and methods for recycling waste plastics

ABSTRACT

Systems and methods for processing waste plastics are provided. One method includes mixing, heating and compacting a supply of the waste plastic based feedstock having an appreciable amount of halide compounds or heteroatoms from one or more sources of contamination; providing an amendment comprising alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum to be mixed, heated and compacted with the waste plastic based feedstock to form a densified melt of plastic material including the amendment; and pyrolyzing the densified melt of plastic material including the amendment within a pyrolysis reactor. Another method includes pyrolyzing a supply of the waste plastic feedstock within a pyrolysis reactor to generate a hydrocarbon gas stream and a solids residue stream; condensing out a tars product from the hydrocarbon gas stream output from the pyrolysis reactor with a quenching apparatus; and pyrolyzing the tars product within a supplemental pyrolysis reactor.

TECHNICAL FIELD

The present disclosure relates generally to the recycling of wasteplastics. Certain embodiments relate more specifically to systems andmethods for pyrolyzing plastic feedstock to convert waste plastics intohydrocarbon based oil products.

BRIEF DESCRIPTION OF THE DRAWINGS

The written disclosure herein describes illustrative embodiments thatare non-limiting and non-exhaustive. Reference is made to certain ofsuch illustrative embodiments that are depicted in the figures, inwhich:

FIG. 1 provides a schematic diagram of an embodiment of a plasticrecycling system; and

FIG. 2 provides a schematic diagram of another embodiment of a plasticrecycling system.

DETAILED DESCRIPTION

Certain embodiments of systems and methods described herein areconfigured for efficient recycling of waste plastics. Some systems andmethods can quickly and simply convert waste plastics into one or morepurified organic molecular species, which can be considered ahydrocarbon oil product. The hydrocarbon oil product may be readilystored, transported, and/or refined into fuel or other commerciallyrelevant materials.

In some embodiments, waste plastic feedstock can be fed continuouslythrough the systems disclosed herein. The feedstock may be pre-meltedvia a mixing, heating and compacting apparatus prior to introductioninto a pyrolysis reactor, which then heats the pre-melted feedstock suchthat the feedstock transitions into a vapor (e.g., one or more gases)for further processing. In some instances, the vapor can be introducedinto a condenser and directly contacted with a pH adjusted solution (orother process solution), which can, in some instances, absorb a portionof the vapor and condense another portion thereof. The condensedmaterial can comprise one or more organic molecular species that can betermed herein as a hydrocarbon oil product. The hydrocarbon oil productcan be separated from the other portions of the vapor that are absorbedinto the pH adjusted solution, and thus the hydrocarbon oil product canbe of a clean or purified quality such that it may be readily refinedfrom a crude state. In other instances, other condensing apparatuses ormethodologies may be used to condense out desirable products from thevapor discharged from the pyrolysis reactor or reactors.

In some instances, the feedstock may comprise waste plastics includingan appreciable amount of halide compounds or heteroatoms from one ormore sources of contamination and the system may be configured torecover a hydrocarbon oil product therefrom. The system may include amixing, heating and compacting apparatus configured to receive a supplyof the waste plastic feedstock and to output a densified melt of plasticmaterial. An amendment comprising or consisting of alkaline earth oxidesand/or hydroxides, oxides of iron, and/or oxides of aluminum may bemixed, heated and compacted with the waste plastic based feedstock inthe mixing, heating and compacting apparatus to form a densified melt ofplastic material including the amendment. The system may furthercomprise a pyrolysis reactor configured to receive the densified melt ofplastic material including the amendment, pyrolyze the densified melt ofplastic material including the amendment, and output a hydrocarbon gasstream and a solids residue stream, the solid residue stream including asubstantial portion of the halide compounds or heteroatoms of the wasteplastic based feedstock via interaction of the halide compounds orheteroatoms with the amendment. Additionally, one or more condensers maybe provided to condense out a hydrocarbon oil product from thehydrocarbon gas stream output from the pyrolysis reactor. In someinstances, the system may be configured to condense out a tars productfrom the hydrocarbon gas stream output from the pyrolysis reactor with aquenching apparatus. The system may be further configured to route thetars product to a secondary pyrolysis reactor to generate a secondaryhydrocarbon gas stream and a secondary solids residue stream. Thesecondary hydrocarbon gas stream may be further processed and combinedwith an altered hydrocarbon gas stream output from the quenchingapparatus for subsequent processing by the one or more condensers torecover a hydrocarbon oil product.

Various illustrative embodiments of inventive systems and methods willnow be described. Advantages of the systems and methods, as well asfeatures and steps thereof, respectively, will be apparent from thedisclosure that follows, including the Figures.

FIG. 1 provides a schematic diagram of an embodiment of a plasticrecycling system 10. The plastic recycling system includes a heatingsystem 12 that is configured to deliver heat to a plastic feedstock 14.The heating system 12 can comprise any suitable heating mechanism, suchas, for example, a combustion burner, a fluidized bed burner, a retort,or any other such heating system. In some instances, the heating systemcomprises a pyrolysis recovery unit (PRU). The PRU may include a dualscrew feed mechanism to receive the plastic feedstock and simultaneouslytransport and pyrolyze the feedstock, and to output a hydrocarbon gasstream 16 and a solids residue stream 18. The PRU may include multiplesuccessive zones of heating along a length thereof.

The plastic feedstock 14 can comprise waste plastics of one or morevarieties (e.g., mixed plastics), and may include trace amounts ofnon-plastic contamination or impurities. For example, the impurities maybe of an external nature (e.g., water, foodstuffs, labeling, soil,paper, or cellulose waste) or may result from internal amendments of thewaste plastics, such as fillers, plasticizers and other amendments,introduced at the time of manufacture of the waste plastics (e.g.,glass, metal, iron, bromine, and/or chlorine). The plastic feedstock 14may be provided in a ground, chipped, or other form that can promote thetransfer of heat thereto.

The plastic feedstock 14 may be fed to the system in a continuousmanner. A feed apparatus can include bins, hoppers, conveyors, mixers,heaters and compactors designed to provide a continuous material feed.The feed apparatus may comprise a mixing, heating and compactingapparatus 20 and may include a compactor and a pre-melter, such as amixer designed to receive the feedstock and output a continuous streamof densified plastic melt. In other instances, the feedstock may be feddirectly into the heating system (e.g., PRU) 12 without being subjectedto pre-melting.

The heat provided by the heating system (e.g., pyrolysis recovery unit)12 can be sufficient to crack or depolymerize the plastic feedstock 14and convert at least a portion thereof into a vapor. The vapor caninclude one or more gaseous organic species, one or more gaseousinorganic species, and/or one or more varieties of entrained particles.In particular, the vapor can include depolymerized non-polar organicgases, which may be desirable for collection and refinement, and whichcan be mixed with impurities. The organic gases can include, forexample, one or more paraffins, olefins, naphthenes, aromatics, and/orother classes of hydrocarbon materials. The mixed-in impurities caninclude, for example, inorganic acids (e.g., hydrochloric acid,hydrobromic acid), entrained metals or metalloids (e.g., cadmium, iron,antimony); and/or organic acids (e.g., terephthalic acid). In someembodiments, the vapor may include additional molecular species, such aspolar organic molecules, which may or may not be collected with thenon-polar organic molecules. For example, the vapor can include one ormore alcohols, ketones, ethers, phenols, carboxylic acids, or otherpolar organic molecules.

In some embodiments, the plastic feedstock may be heated under vacuumconditions, or under negative pressure. In other embodiments, theplastic feedstock may be heated under positive pressure. In still otheror further embodiments, the plastic feedstock may be heated underatmospheric pressure conditions, or under any suitable combination ofthe foregoing (e.g., the pressure may be varied during a heating event).

The vapor can be delivered to a vapor treatment system 22 that effects aphase change of at least a portion of the vapor such that certainmolecules transition from a gaseous state to a liquid state. The vaportreatment system 22 may also be referred to as a vapor treatment unit ora vapor treatment vessel. The vapor treatment system 22 may include a pHadjusted solution (or other process solution) that is used to effect thecondensation. Moreover, the pH adjusted solution can be configured toabsorb at least a portion of the impurities from the vapor. Embodimentsof the solution can readily absorb organic acids, inorganic acids,metals, metalloids, and/or certain polar organic molecules. The term “pHadjusted solution” is used in a broad sense and includes solutions thatare not pH neutral and that exhibit any or all of the various propertiesdescribed herein. For example, a pH adjusted solution can be formulatedto remove impurities from the vapor, and in further embodiments, can beimmiscible with condensed oils so as to be readily separated therefrom.For example, in some embodiments, the pH adjusted solution can comprisean acidic solution, which may, in some cases, be strongly acidic. Infurther embodiments, the pH adjusted solution can comprise a bufferedaqueous solution adjusted to a desired pH value. In various embodiment,the pH adjusted solution can have a pH value that is less than 7, lessthan about 6.5, less than about 6, less than about 5.5, less than about5, less than about 4, or less than about 3.

The pH adjusted solution can include one or more chemical amendments ofany suitable variety to achieve the desired properties of the solution.Such properties can include, for example, the ability to remove one ormore impurities from the vapor and/or a high immiscibility with oil.Adjustment or optimization of one or more of foregoing properties may beachieved by altering the concentration of the one or more chemicalamendments within the pH adjusted solution. For example, the presence,combination, and/or concentration of one or more materials within the pHadjusted solution can optimize removal of contaminants from the vapor asit interacts with the pH adjusted solution. In various embodiments, thepH adjusted solution can include strong and/or weak inorganic acids(e.g., hydrochloric acid, acetic acid), one or more pH buffer solutions(e.g., acetic acid+sodium acetate), one or more chelating agents (e.g.,ethylenediaminetetraacetic acid (EDTA)), and/or one or more coagulantsand/or flocculants (e.g., calcium hydroxide, polyacrylamide).

The vapor treatment system 22 can be configured to effect direct contactbetween the vapor received therein and the pH adjusted solution (orother process solution). For example, as further discussed below, insome embodiments, the pH adjusted solution may be sprayed into contactwith the vapor, whereas in other embodiments, the vapor may be bubbledthrough the solution. The pH adjusted solution can absorb or dissolveportions of the vapor (e.g., organic acids, inorganic acids, metals,metalloids, and/or certain polar organic molecules). The pH adjustedsolution also can be provided at a lower temperature than that of thevapor such that the solution condenses at least those portions of thevapor that are immiscible therein (e.g., non-polar organic molecules).

Those portions of the condensed vapor that are immiscible in the pHadjusted solution (i.e., the hydrophobic portions) can be readilyseparated from the solution. In some embodiments, the separation (or atleast one or more stages thereof) takes place within the vapor treatmentsystem, whereas in other embodiments, the separation (or at least one ormore stages thereof) takes place within a separator 24 that isindependent of the vapor treatment system 22.

In some embodiments, the immiscible portions are removed from the vaportreatment system as a form of crude oil 26. The crude oil 26 thus canhave few or no impurities, as the impurities that were present in theplastic feedstock are dissolved or absorbed into the pH adjustedsolution. In some embodiments, at least some of the dissolved orabsorbed impurities can remain within the pH adjusted solution withinthe vapor treatment system 22. For example, in some instances, after thepH adjusted solution has amassed the impurities, it may continue to beused within the vapor treatment system 22, such that the impurities arenot removed (at least not immediately) from the vapor treatment system22. In other or further embodiments, dissolved or absorbed impuritiesare removed from the vapor treatment system 22 separately from the oil26.

Certain classes of polar organic molecules may only partially (or atleast partially) partition into the pH adjusted solution. For example, aportion of certain alcohols, ketones, ethers, phenols, carboxylic acids,and/or other polar organic molecules may partition into the pH adjustedsolution and another portion thereof may partition into the crude oil.Accordingly, in some embodiments, crude oil that includes a portion of aspecies of polar organic molecules may be separated from a pH adjustedsolution that contains another portion of the species of polar organicmolecules.

The vapor may include portions that do not condense within the vaportreatment system 22 and are not absorbed by the pH adjusted solution.Such non-condensable gases 29 can be removed separately from the vaportreatment system 22, and may be combusted or disposed of in any othersuitable manner.

In various embodiments, the vapor treatment system 22 may operate undervacuum conditions, or under negative pressure. In other embodiments, thevapor treatment 22 system may operate under positive pressure. In stillother or further embodiments, the vapor treatment system 22 may operateunder atmospheric pressure conditions, or under any suitable combinationof the foregoing (e.g., the pressure may be varied during a condensingevent).

The system can be well suited for quickly cracking or depolymerizing theplastic feedstock. For example, in some embodiments, heating of theplastic feedstock and conversion thereof into the vapor can be performedat high temperatures at which a variety of different molecular speciesmay be gasified simultaneously. Such different molecular species mighthave different vaporization temperatures at a given pressure, and atemperature at which the plastic feedstock is heated can exceed thistemperature for some or all of the molecular species. The molecularspecies can then be separated from each other when the vapor isdelivered to the vapor treatment system, as previously described.Accordingly, the system can operate without the heating system slowlyheating up and occasionally holding steady at various discreettemperature levels along the way so as to allow for individual molecularspecies to be gasified sequentially. It is to be appreciated, however,the system may also be used in an operational mode in which the heatingsystem and the plastic feedstock progress through a series of sequentialheating steps or levels, as just described.

The system 10 can include a vacuum system 30 that is configured tomaintain a negative pressure within the heating system (e.g., PRU) 12and within the vapor treatment system 22. The vacuum system 30 cancontinuously evacuate gases from the heating system (e.g., PRU) 12 suchthat depolymerization of the plastic feedstock occurs in anoxygen-deprived or oxygen-free environment. The vacuum system 30 drawsthe vapor into the vapor treatment system 22, where it is contacted bythe pH adjusted solution, or non-PH adjusted solution, or otherwiseprocessed by a condensing apparatus or device. The vacuum system 30draws the non-condensable gases 29 from the vapor treatment system 22,and may distribute them to a combustion unit or other suitable disposaldevice 32 (e.g., emissions control device). In some instances, thenon-condensable gases 29 from the vapor treatment system 22 may berouted to a heat exchanger or other apparatus or system for energyrecovering purposes. For instance, the non-condensable gases 29 from thevapor treatment system 22 may be routed to a heat exchanger to supplyheat for other aspects of the systems and methods of processing wasteplastics described herein, such as, for example, supplying heat to themixing, heating and compacting apparatus 20 (e.g., pre-melt extruder) toassist in generating the densified plastic melt for introduction intothe heating system (PRU) 12. In other instances, the non-condensablegases 29 from the vapor treatment system 22 may be routed to a heatexchanger or other energy recovery device to supply energy for otherunrelated purposes.

The system 10 may include a coalescer/separator 24 that receives anemulsion of condensed material from the vapor treatment system 22. Theemulsion can comprise crude oil that includes a small amount of the pHadjusted solution (or other process solution) entrained therein. Thecoalescer/separator 24 can be configured to separate the crude oil 26from the pH adjusted solution (or other process solution) based on thedifference in relative density between these materials. For example, thecoalescer/separator 24 can comprise a settling tank that allowsgravitational separation of the solution from the crude oil 26. In otherembodiments, the coalescer/separator 24 may comprise a centrifuge orother separator device.

The system 10 can further include a variety of sensor and controlcomponents (not shown). For example, the system 10 can include one ormore pressure sensors and/or temperature sensors, which can provide to acontroller various data regarding the operation of the heating system(e.g., PRU) 12 and the amount of heat being delivered to the feedstock.The sensors can communicate with a controller in any suitable manner,such as by wired or wireless connection. The controller can alteroperational parameters of the heating system (e.g., PRU) 12 in responseto data received from the sensors and/or as a result of otherprogramming.

A master control system may be configured to communicate with thecontroller, and may also be configured to communicate with additionalcontrollers that may each be dedicated to subsystems of the plasticrecycling system. For example, separate subsystem controllers may bededicated to the vapor treatment system 22 and the vacuum system 30,respectively. In some embodiments, subsystem controllers may be situatedlocally (e.g., near the various subsystems with which they areassociated), whereas the master control system may be situated in asupervisory station in which an operator can monitor the instantaneousstatus of the subsystems of the system 10 and make changes thereto asdesired, whether onsite or offsite.

For the sake of convenience, subsystem controller(s) associated with aparticular component may not be identified hereafter, nor will it beexplicitly stated that a particular subsystem controller and/or themaster control system is able to monitor and/or control the operation ofa particular component of the plastic recycling system 10, although suchis understood. It is also noted that steps or control events discussedherein which can be effected by sub-controllers and/or the mastercontrol system may be embodied in machine-executable instructions thatare to be executed by a general-purpose or special-purpose computer (orother electronic device). Alternatively, the steps or control events maybe performed or instigated by hardware components that include specificlogic for performing the steps or control events, or by a combination ofhardware, software, and/or firmware. Some or all of the steps may beperformed locally (e.g., via a subsystem controller) or remotely.

As the feedstock is heated in the heating system (e.g., PRU) 12, theplastic feedstock eventually gasifies or vaporizes. The vapor can beintroduced into the vapor treatment system 22 in any suitable manner.For example, in some embodiments, the vapor may be introduced into acondensing tower of a condenser substantially without altering atrajectory of the vapor. In other embodiments, the vapor may encounter abaffle upon entering the condensing tower.

Those portions of the vapor that are not condensed (i.e.,non-condensable gases) may be passed to a caustic scrubber, which passesthe remaining vapor through a caustic solution so as to chemically scrubthe vapor (e.g., remove mercaptan sulfur species therefrom) and so as toneutralize trace levels of free inorganic acids. The remainder of thevapor may pass from the caustic scrubber through to an emissions controldevice (ECD) 32. Any suitable vacuum system 30 may be used with theplastic recycling system 10 to move the vapor accordingly.

Any suitable emissions control device (ECD) 32 can be used with theplastic recycling system 10. In some embodiments, the emissions controldevice 32 can comprise a burner or other combustion device. Exhaust 34from the emissions control device 32 may be vented to atmosphere. Inother embodiments, the hot exhaust 34 may instead be transferred toother portions of the plastic recycling system 10.

The absorbed and condensed portions of the vapor may settle into a tankof the coalescer/separator 24 that includes one or more weirs. The pHadjusted solution (or other process solution), which retains theabsorbed impurities, may facilitate coagulation of some contaminantswhich have a greater relative density than the condensed crude oilmaterial 26, and may settle to the bottom of the tank. Accordingly, thecondensed crude oil 26 rises to the top of the tank and flows over theone or more weirs to be collected for further processing 36, storage 38or use.

In addition, downstream processing may be provided in some embodimentsto purify the product streams discussed herein or fractionate saidstreams into specified hydrocarbon cuts. Process units for this purposemay include, but are not limited to, distillation, solvent extraction,adsorption, and catalyst treatment units.

In some instances, one or more supplemental condensers 40 may beprovided to condense out light hydrocarbons 42 from the quenchedpyrolysis gas 28. The one or more streams of light hydrocarbons 42 maythen be combined with the crude oil product 26, or may be stored asseparate hydrocarbon products. In some instances, at least a portion 43of the light hydrocarbons 42 may be directed to the vapor treatmentsystem 22 to assist in quenching the pyrolysis gases, namely, thehydrocarbon gas stream 16 output from the heating system (e.g., PRU) 12.In some instances, at least a portion 43 of the light hydrocarbons 42may be directed to the heating system (e.g., PRU) 12 to be reintroducedinto the heating system (e.g., PRU) 12 for further processing.

FIG. 2 provides a schematic diagram of another embodiment of a plasticrecycling system 100, which is particularly well suited for producingone or more hydrocarbon oil products 126, 143 from waste plasticfeedstock 114. Similar to the aforementioned system, a mixing, heatingand compacting apparatus (e.g., pre-melt extruder) 120 may be providedto receive a supply of waste plastic 114 and to output a densified meltof plastic material 121. The system 100 may further include a pyrolysisrecovery unit (PRU) 112 that is configured to receive the densified meltof plastic material 121 and pyrolyze the densified melt of plasticmaterial 121 and output a primary hydrocarbon gas stream 116 and aprimary solids residue stream 118. The PRU 112 may comprise, forexample, a dual screw feed mechanism within a reactor shell which isconfigured to simultaneously transport and heat the feedstock introducedinto the PRU 112. The PRU 112 may have multiple zones of heating along alength thereof to effectively heat the feedstock to a pyrolysistemperature as the material progresses from one end of the PRU 112 tothe other.

The system 100 may further comprise a primary quenching apparatus 122that is configured to receive the hydrocarbon gas stream 116 output fromthe PRU 112 and to condense out a tars product 123 for introduction intoa supplemental tars pyrolysis reactor 160 for further processing, asdiscussed elsewhere herein. Similar to the PRU 112, the supplementaltars pyrolysis reactor 160 may comprise a dual screw feed mechanismwithin a reactor shell which is configured to simultaneously transportand heat the material introduced into the supplemental tars pyrolysisreactor 160. The supplemental tars pyrolysis reactor 160 may havemultiple zones of heating along a length thereof to effectively heat thefeedstock to a pyrolysis temperature as the material progresses from oneend of the supplemental tars pyrolysis reactor 160 to the other. The PRU112 and the supplemental tars pyrolysis reactor 160 may have differentform factors, throughput capacities and/or different heating profiles.

The primary quenching apparatus 122 may also be configured to dischargean altered hydrocarbon gas stream 128 for further processing. A primarycondenser and separator 140 may be provided to receive the alteredhydrocarbon gas stream 128 from the primary quenching apparatus 122 andto condense out and separate a hydrocarbon oil product 126.Additionally, a supplemental condenser and separator 141 may be providedto receive a discharged gas stream 142 from the primary condenser andseparator 140 and to condense out and separate light hydrocarbons (e.g.,methane, ethane, propane) to form a light hydrocarbon product 143 or tobe combined with other product streams. The primary condenser andseparator 140 and/or the supplemental condenser and separator 141 may beconfigured to direct a portion of the hydrocarbon oil product 126 andthe light hydrocarbon product 143 upstream to the primary quenchingapparatus 122 to assist in condensing out the tars product 123 from thehydrocarbon gas stream 116 output from the PRU 112. In some instances,at least a portion of the hydrocarbon oil product 126 and/or at least aportion of the light hydrocarbon product 143 may be directed to theheating system (e.g., PRU) 12 to be reintroduced into the heating system(e.g., PRU) 12 for further processing.

Any remaining non-condensable gasses 129 may be processed as describedin connection with the aforementioned system, including processing by anappropriate emissions control device 132 and under the influence of avacuum system 130. In some instances, the non-condensable gases 129 fromthe vapor treatment system 22 may be routed to a heat exchanger or otherapparatus or system for energy recovering purposes. For instance, thenon-condensable gases 129 from the vapor treatment system 22 may berouted to a heat exchanger to supply heat for other aspects of thesystems and methods of processing waste plastics described herein, suchas, for example, supplying heat to the mixing, heating and compactingapparatus 20 (e.g., pre-melt extruder) to assist in generating thedensified plastic melt for introduction into the heating system (PRU)12. In other instances, the non-condensable gases 129 from the vaportreatment system 22 may be routed to a heat exchanger or other energyrecovery device to supply energy for other unrelated purposes.

Although multiple stage condenser/separators are shown and describedherein, it is appreciated that the systems and methods described hereinare not limited to the use of multiple stage condensing and separating,and may, in other instances, include a single stage condensing andseparating apparatus or employ other well know systems and techniquesfor condensing and separating out one or more desired products, such asthrough distillation techniques and the like.

The hydrocarbon oil product stream may be filtered and chilled by aproduct filter 150 and a product chiller 151 prior to product storage ortransport. In addition, downstream processing may be provided in someembodiments to purify the product streams discussed herein orfractionate said streams into specified hydrocarbon cuts. Process unitsfor this purpose may include, but are not limited to, distillation,solvent extraction, adsorption, and catalyst treatment units.

As discussed above, the system 100 may comprise a primary quenchingapparatus 122 that is configured to receive the hydrocarbon gas stream116 output from the PRU 112 and to condense out a tars product 123 forrouting to a tars pyrolysis reactor 160 for further processing. A supplyof the tars product 123 may be temporarily stored in a tars tank 162 forsubsequent processing or use. A portion of the tars product 123 may bebled off from the system 100 and routed via a tars bleed line 164 to anenergy recovery unit or to an appropriate disposal system. At least someof the tars product 123 may be routed to the tars pyrolysis reactor 160for pyrolysis of the tars product 123 into a secondary hydrocarbon gasstream 166 and a secondary solids residue stream 168. The secondarysolids residue stream 168 may be combined with the primary solidsresidue stream 118 and routed to an appropriate waste disposal system169.

Advantageously, the system 100 may further comprise a secondaryquenching apparatus 170 that is configured to receive the secondaryhydrocarbon gas stream 166 output from the tars pyrolysis reactor 160and to condense out a supplemental hydrocarbon product 172. Thesupplemental hydrocarbon product 172 may be combined with the tarsproduct 123 output from the primary quenching apparatus 122 for reentryinto the tars pyrolysis reaction 160 for further processing as discussedabove. In this manner, a portion of the feedstock can be continuouslyrefined by the tars pyrolysis reactor 160 to provide an exceptionallypurified hydrocarbon based oil product.

The secondary quenching apparatus 170 may also be configured todischarge a supplemental altered hydrocarbon gas stream 174. Thesupplemental altered hydrocarbon gas stream 174 may be combined with thealtered hydrocarbon gas stream 128 from the primary quenching apparatus122 and routed to the primary and secondary condenser and separators140, 141 for further processing as discussed above. In addition, thesecondary quenching apparatus 170 may be configured to receive a portionof the hydrocarbon oil product 126 and/or the light hydrocarbon product143 from the condenser and separators 140, 141 to assist in condensingout the supplemental hydrocarbon product 172 from the secondaryhydrocarbon gas stream 166 output from the tars pyrolysis reactor 160.

In accordance with some aspects of the present invention, a supply ofthe waste plastic feedstock may include an appreciable amount of halidecompounds (e.g., hydrogen chloride) or heteroatoms (e.g., sulfur,phosphorous) from one or more sources of contamination (e.g., halidecontaining plastics such as PVC, polymer additives, contaminants fromfood, soil, salt and other environmental sources). Advantageously,embodiments of the systems described herein may include an amendmentfeed arrangement 180 to enable the introduction of an amendment 181 tothe feedstock to be pyrolyzed with the waste plastic material 114 andany contaminants therein. The amendment 181 may comprise, for example,alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxidesof aluminum. In particular, the amendment 181 may comprise, for example,at least one of: calcium oxide (CaO); calcium hydroxide (Ca(OH)₂);ferric oxide (Fe₂O₃); and alumina (Al₂O₃). The amendment 181 may beprovided in the form of: a homogenous powder or particles; supportedmaterial on a solid substrate; or a slurry. For example, the amendment181 may be provided in the form of a slurry having a solvent in the formof water, a hydrocarbon, or a hydrocarbon mixture. The amendment 181 maybe provided in a concentration of between 1% and 10% by weight of thecombined waste plastic feedstock and amendment, or between 3% and 4% byweight of the combined waste plastic feedstock and amendment, or about3.5% by weight of the combined waste plastic feedstock and amendment.

Advantageously, the amendment 181 may be combined with the waste plasticbased feedstock prior to mixing, heating and compacting of the supply ofthe waste plastic based feedstock 114 to form the densified melt ofplastic material 121. For example, the supply of the waste plastic basedfeedstock 114 and the amendment 181 may be mixed, compacted and heatedto at least about 200 degrees Celsius prior to introduction in thepyrolysis reactor 112 to provide a particularly advantageous densifiedmelt of plastic material having the amendment interspersed therein. Inaddition, the waste plastic based feedstock 114 and the amendment 181may be fed through an airlock 182 to substantially reduce or eliminateoxygen from the waste plastic based feedstock 114 and the amendment 181.In this manner, the densified melt of plastic material 121 may comprisethe amendment intermixed throughout the densified melt of plasticmaterial 121 prior to supplying of the densified melt of plasticmaterial 121 to the pyrolysis reactor 112 under oxygen free or lowoxygen conditions. Although the airlock 182 is illustrated schematicallyas a separate component or sub-system, the airlock 182 may be integratedinto the mixing, heating and compacting apparatus (e.g., pre-meltextruder) 120, when provided, or into the pyrolysis reactor 112 toprovide oxygen free or low oxygen conditions within the pyrolysisreactor 112 during pyrolysis.

The amendment 181 may be mixed with the waste plastic based feedstock114 prior to introduction into the mixing, heating and compactingapparatus (e.g., pre-melt extruder) 120, or may be mixed with the wasteplastic based feedstock within the mixing, heating and compactingapparatus (e.g., pre-melt extruder) 120 itself. In other lessadvantageous instances, the amendment 181 may be fed into the pyrolysisreactor 112 separate from the densified melt of plastic material 121 tobe mixed with the plastic material within the pyrolysis reactor 112itself. Still further, in embodiments where the mixing, heating andcompacting apparatus (e.g., pre-melt extruder) 120 may be omitted, theamendment 181 may be combined with the waste plastic based feedstock 114and may forgo pre-melting prior to introduction of the materials intothe pyrolysis reactor 112.

In any event, upon pyrolysis of the waste plastic feedstock 114intermixed with the amendment 181, the pyrolysis reactor 112 isconfigured to output the hydrocarbon gas stream 116 for processing (asdiscussed above) and the solids residue stream 118. Advantageously, insuch instances, the solid residue stream 118 includes a substantialportion of the halide compounds or heteroatoms of the waste plasticbased feedstock 114 via interaction of the halide compounds orheteroatoms with the amendment 181. As such, the addition of theamendment 181 can assist to provide an exceptionally purifiedhydrocarbon based oil product by effectively removing halide compoundsand heteroatoms from the product streams.

In view of the foregoing, it will be appreciated that various methods ofprocessing waste plastics may be provided.

According to one example embodiment, a method of processing wasteplastics may be summarized as including: mixing, heating and compactinga supply of a waste plastic based feedstock including an appreciableamount of halide compounds or heteroatoms from one or more sources ofcontamination; providing an amendment comprising alkaline earth oxidesand/or hydroxides, oxides of iron, and/or oxides of aluminum to bemixed, heated and compacted with the waste plastic based feedstock toform a densified melt of plastic material including the amendment;supplying the densified melt of plastic material including the amendmentto a pyrolysis reactor; pyrolyzing the densified melt of plasticmaterial including the amendment within the pyrolysis reactor togenerate a hydrocarbon gas stream and a solids residue stream, the solidresidue stream including a substantial portion of the halide compoundsor heteroatoms of the waste plastic based feedstock via interaction ofthe halide compounds or heteroatoms with the amendment; and condensingout the hydrocarbon based product from the hydrocarbon gas stream outputfrom the pyrolysis reactor.

Providing the amendment may include mixing the amendment with the wasteplastic based feedstock prior to or during the mixing, heating andcompacting of the supply of the waste plastic based feedstock to formthe densified melt of plastic material, such that the densified melt ofplastic material comprises the amendment intermixed throughout thedensified melt of plastic material prior to supplying of the densifiedmelt of plastic material including the amendment to the pyrolysisreactor.

The method may further include, prior to mixing, heating and compactingthe supply of the waste plastic based feedstock and the amendment,passing the supply of the waste plastic based feedstock and theamendment through an airlock to substantially reduce or eliminate oxygenfrom the waste plastic based feedstock and the amendment.

The method may further include condensing out a tars product from thehydrocarbon gas stream output from the pyrolysis reactor with aquenching apparatus and routing the tars product to a secondarypyrolysis reactor distinct from the pyrolysis reactor to generate asecondary hydrocarbon gas stream and a secondary solids residue stream.The method may further include condensing out a hydrocarbon product fromthe secondary hydrocarbon gas stream output from the secondary pyrolysisreactor with a secondary quenching apparatus and routing the hydrocarbonproduct to the secondary pyrolysis reactor for further processing. Stillfurther, the method may include: discharging an altered hydrocarbon gasstream from the quenching apparatus; discharging a supplemental alteredhydrocarbon gas stream from the secondary quenching apparatus; andcombining the altered hydrocarbon gas stream from the quenchingapparatus and the supplemental altered hydrocarbon gas stream from thesecondary quenching apparatus for further processing by one or morecondensers.

Another example embodiment of a method of processing waste plastics maybe summarized as including: pyrolyzing a supply of a waste plasticfeedstock within a primary pyrolysis reactor to generate a primaryhydrocarbon gas stream and a primary solids residue stream; condensingout a tars product from the primary hydrocarbon gas stream output fromthe primary pyrolysis reactor with a primary quenching apparatus;discharging a primary altered hydrocarbon gas stream from the primaryquenching apparatus; pyrolyzing the tars product within a secondarypyrolysis reactor to generate a secondary hydrocarbon gas stream and asecondary solids residue stream; condensing out a supplementalhydrocarbon product from the secondary hydrocarbon gas stream outputfrom the secondary pyrolysis reactor with a secondary quenchingapparatus; discharging a supplemental altered hydrocarbon gas streamfrom the secondary quenching apparatus; combining the supplementalaltered hydrocarbon gas stream from the secondary quenching apparatuswith the primary altered hydrocarbon gas stream from the primaryquenching apparatus to form a combined altered hydrocarbon gas stream;and condensing out a hydrocarbon oil product from the combined alteredhydrocarbon gas stream with one or more condensers. The method mayfurther include routing the supplemental hydrocarbon product from thesecondary quenching apparatus to the secondary pyrolysis reactor forfurther processing.

Furthermore, the method may include: mixing, heating and compacting thesupply of the waste plastic feedstock to form a densified melt ofplastic material; and supplying the densified melt of plastic materialto the primary pyrolysis reactor. In some instances, the method mayfurther include providing an amendment comprising alkaline earth oxidesand/or hydroxides, oxides of iron, and/or oxides of aluminum to bemixed, heated and compacted with the waste plastic based feedstock forintroduction into the pyrolysis reactor. In yet other instances, themethod may further include providing an amendment comprising alkalineearth oxides and/or hydroxides, oxides of iron, and/or oxides ofaluminum to be combined with the waste plastic feedstock for pyrolysistreatment within the primary pyrolysis reactor without pre-melting.

It is appreciated that aspects of the systems and methods describedherein may be applicable to treating mixed waste plastics comprising avariety of plastics types, or treating a mixed waste plastic feedstockthat may be characterized by including predominantly one or moreparticular waste plastics, such as, for example, a feedstock ofpredominately waste polystyrene from which a monomer (i.e., styrene)product may be recovered.

It is also appreciated that aspects of the systems and methods describedherein may include the aforementioned mixing, heating and compactingapparatus (e.g., pre-melt extruder) 20, 120 to receive a supply of wasteplastic and to output a densified melt of plastic material, or, in otherinstances, the feedstock may be fed directly into the heating system orpyrolysis reactor (e.g., PRU) 12, 112 without being subjected topre-melting.

Still further, it is appreciated that various product streams generatedthroughout the systems and methods described herein, may be routed backto the heating system or pyrolysis reactor (PRU) 12, 112 to bereintroduced into the heating system or pyrolysis reactor (PRU) 12, 112for further processing, or may by routed elsewhere or sold as a separateproduct with or without additional conditioning of said product streams.

Additional components, features and functionality of the systems will bereadily apparent to those of ordinary skill in the relevant art upon areview of the detailed schematic diagrams provided in the Figures.

Moreover, it will be understood by those having ordinary skill in therelevant art that changes may be made to the details of the embodimentsdescribed and illustrated herein without departing from the underlyingprinciples presented herein. For example, any suitable combination ofvarious embodiments, or the features thereof, is contemplated. Forexample, various embodiments may be configured to operate in one or moreof a batch mode, a continuous batch mode, or a continuous mode. Other orfurther embodiments may include a condenser system and/or othercomponents that are configured to operate under one or more of vacuumconditions, atmospheric pressure conditions, or positive pressureconditions.

Any methods disclosed herein comprise one or more steps or actions forperforming the described method. The method steps and/or actions may beinterchanged with one another. In other words, unless a specific orderof steps or actions is required for proper operation of the embodiment,the order and/or use of specific steps and/or actions may be modified.

Throughout this specification, any reference to “one embodiment,” “anembodiment,” or “the embodiment” means that a particular feature,structure, or characteristic described in connection with thatembodiment is included in at least one embodiment. Thus, the quotedphrases, or variations thereof, as recited throughout this specificationare not necessarily all referring to the same embodiment.

Similarly, it should be appreciated that in the above description ofembodiments, various features are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure. This method of disclosure, however, is notto be interpreted as reflecting an intention that any claim require morefeatures than those expressly recited in that claim. Rather, inventiveaspects lie in a combination of fewer than all features of any singleforegoing disclosed embodiment. It will be apparent to those havingskill in the art that changes may be made to the details of theabove-described embodiments without departing from the underlyingprinciples set forth herein.

U.S. Provisional Patent Application No. 63/123,965, filed Dec. 10, 2020,is incorporated herein by reference, in its entirety.

The invention claimed is:
 1. A method of processing a waste plasticbased feedstock to form a hydrocarbon based product, the methodcomprising: mixing, heating and compacting a supply of the waste plasticbased feedstock, the waste plastic based feedstock including halidecompounds or heteroatoms from one or more sources of contamination;providing at least one amendment selected from the group consisting ofalkaline earth oxides, alkaline earth hydroxides, oxides of iron, andoxides of aluminum to be mixed, heated and compacted with the wasteplastic based feedstock to form a densified melt of plastic materialincluding the amendment; prior to mixing, heating and compacting thesupply of the waste plastic based feedstock and the amendment, passingthe supply of the waste plastic based feedstock and the amendmentthrough an airlock to substantially reduce or eliminate oxygen from thewaste plastic based feedstock and the amendment; supplying the densifiedmelt of plastic material including the amendment to a pyrolysis reactor;pyrolyzing the densified melt of plastic material including theamendment within the pyrolysis reactor to generate a hydrocarbon gasstream and a solids residue stream, the solid residue stream including asubstantial portion of the halide compounds or heteroatoms of the wasteplastic based feedstock via interaction of the halide compounds orheteroatoms with the amendment; and condensing out the hydrocarbon basedproduct from the hydrocarbon gas stream output from the pyrolysisreactor.
 2. The method of claim 1 wherein the amendment is selected fromthe group consisting of calcium oxide (CaO); calcium hydroxide(Ca(OH)₂); ferric oxide (Fe₂O₃); and alumina (Al₂O₃).
 3. The method ofclaim 1 wherein providing the amendment includes mixing the amendmentwith the waste plastic based feedstock prior to the mixing, heating andcompacting of the supply of the waste plastic based feedstock to formthe densified melt of plastic material including the feed amendment, andwherein the densified melt of plastic material comprises the amendmentintermixed throughout the densified melt of plastic material prior tosupplying of the densified melt of plastic material including theamendment to the pyrolysis reactor.
 4. The method of claim 1 whereinproviding the amendment includes mixing the amendment with the wasteplastic based feedstock during the mixing, heating and compacting of thesupply of the waste plastic based feedstock to form the densified meltof plastic material including the feed amendment, and wherein thedensified melt of plastic material comprises the amendment intermixedthroughout the densified melt of plastic material prior to supplying ofthe densified melt of plastic material including the feed amendment tothe pyrolysis reactor.
 5. The method of claim 1 wherein the amendment isa homogenous powder or particles; supported material on a solidsubstrate; or a slurry.
 6. The method of claim 5 wherein the amendmentis added to water, a hydrocarbon, or a hydrocarbon mixture forming aslurry.
 7. The method of claim 1 wherein providing the amendmentincludes providing the amendment in a concentration of between 1% and10% by weight of the combined waste plastic feedstock and amendment. 8.The method of claim 7 wherein providing the amendment includes providingthe amendment in a concentration of between 3% and 4% by weight of thecombined waste plastic feedstock and amendment.
 9. The method of claim 1wherein mixing, heating and compacting a supply of the waste plasticbased feedstock and the amendment includes heating the supply of thewaste plastic based feedstock and the amendment to at least about 200degrees Celsius prior to introduction in the pyrolysis reactor.
 10. Themethod of claim 1 wherein the pyrolysis reactor is a primary pyrolysisreactor, and wherein the method further comprises: condensing out a tarsproduct from the hydrocarbon gas stream output from the primarypyrolysis reactor with a primary quenching apparatus and routing thetars product to a secondary pyrolysis reactor distinct from the primarypyrolysis reactor to generate a secondary hydrocarbon gas stream and asecondary solids residue stream.
 11. The method of claim 10, furthercomprising: condensing out a hydrocarbon product from the secondaryhydrocarbon gas stream output from the secondary pyrolysis reactor witha secondary quenching apparatus and routing the hydrocarbon product tothe secondary pyrolysis reactor for further processing.
 12. The methodof claim 10, further comprising: discharging an altered hydrocarbon gasstream from the primary quenching apparatus; discharging a supplementalaltered hydrocarbon gas stream from the secondary quenching apparatus;and combining the altered hydrocarbon gas stream from the primaryquenching apparatus and the supplemental altered hydrocarbon gas streamfrom the secondary quenching apparatus for further processing by one ormore condensers.
 13. A system for processing a waste plastic basedfeedstock, the system comprising: a mixing, heating and compactingapparatus configured to receive a supply of the waste plastic feedstockand to output a densified melt of plastic material, the waste plasticbased feedstock including halide compounds or heteroatoms from one ormore sources of contamination; an amendment feed arrangement forproviding at least one amendment selected from the group consisting ofalkaline earth oxides, alkaline earth hydroxides, oxides of iron, andoxides of aluminum to be mixed, heated and compacted with the wasteplastic based feedstock in the mixing, heating and compacting apparatusto form a densified melt of plastic material including the amendment; apyrolysis reactor configured to receive the densified melt of plasticmaterial including the amendment, pyrolyze the densified melt of plasticmaterial including the amendment, and output a hydrocarbon gas streamand a solids residue stream, the solid residue stream including asubstantial portion of the halide compounds or heteroatoms of the wasteplastic based feedstock via interaction of the halide compounds orheteroatoms with the amendment; an airlock located upstream of themixing, heating and compacting apparatus to substantially reduce oreliminate oxygen from the waste plastic based feedstock and theamendment; and at least one condenser configured to condense out ahydrocarbon based oil product from the hydrocarbon gas stream outputfrom the pyrolysis reactor.
 14. The system of claim 13, furthercomprising: a primary quenching apparatus configured to receive thehydrocarbon gas stream output from the pyrolysis reactor and condenseout a tars product, and to discharge a primary altered hydrocarbon gasstream; a secondary pyrolysis reactor configured to receive the tarsproduct, pyrolyze the tars product, and output a secondary hydrocarbongas stream and a secondary solids residue stream; and a secondaryquenching apparatus configured to receive the secondary hydrocarbon gasstream output from the secondary pyrolysis reactor and condense out asupplemental hydrocarbon product, and to discharge a supplementalaltered hydrocarbon gas stream, and wherein the at least one condenseris configured to receive the primary altered hydrocarbon gas stream andthe supplemental altered hydrocarbon gas stream from the primary andsecondary quenching apparatuses and condense out the hydrocarbon basedoil product.
 15. The system of claim 14 wherein a recycling line isarranged to route the supplemental hydrocarbon product from thesecondary quenching apparatus to the secondary pyrolysis reactor forfurther processing.
 16. A method of processing a waste plasticfeedstock, the method comprising: pyrolyzing a supply of the wasteplastic feedstock within a primary pyrolysis reactor to generate aprimary hydrocarbon gas stream and a primary solids residue stream;condensing out a tars product from the primary hydrocarbon gas streamoutput from the primary pyrolysis reactor with a primary quenchingapparatus; discharging a primary altered hydrocarbon gas stream from theprimary quenching apparatus; pyrolyzing the tars product within asecondary pyrolysis reactor to generate a secondary hydrocarbon gasstream and a secondary solids residue stream; condensing out asupplemental hydrocarbon product from the secondary hydrocarbon gasstream output from the secondary pyrolysis reactor with a secondaryquenching apparatus; discharging a supplemental altered hydrocarbon gasstream from the secondary quenching apparatus; combining thesupplemental altered hydrocarbon gas stream from the secondary quenchingapparatus with the primary altered hydrocarbon gas stream from theprimary quenching apparatus to form a combined altered hydrocarbon gasstream; and condensing out a hydrocarbon oil product from the combinedaltered hydrocarbon gas stream with one or more condensers.
 17. Themethod of claim 16, further comprising: routing the supplementalhydrocarbon product from the secondary quenching apparatus to thesecondary pyrolysis reactor for further processing.
 18. The method ofclaim 16, further comprising: mixing, heating and compacting the supplyof the waste plastic feedstock to form a densified melt of plasticmaterial; and supplying the densified melt of plastic material to theprimary pyrolysis reactor.
 19. The method of claim 18 wherein the supplyof the waste plastic feedstock includes halide compounds or heteroatomsfrom one or more sources of contamination, and wherein the methodfurther comprises: providing at least one amendment selected from thegroup consisting of alkaline earth oxides, alkaline earth hydroxides,oxides of iron, and oxides of aluminum to be mixed, heated and compactedwith the waste plastic based feedstock for introduction into the primarypyrolysis reactor.
 20. The method of claim 19 wherein, during thepyrolyzing, the amendment in the waste plastic feedstock chemicallyinteracts with the halide compounds or heteroatoms of the waste plasticbased feedstock to remove at least a substantial portion of the halidecompounds or heteroatoms from the primary hydrocarbon gas stream. 21.The method of claim 16, wherein the supply of the waste plasticfeedstock includes halide compounds or heteroatoms from one or moresources of contamination, and wherein the method further comprises:providing at least one amendment selected from the group consisting ofalkaline earth oxides, alkaline earth hydroxides, oxides of iron, andoxides of aluminum to be combined with the waste plastic feedstock forpyrolysis treatment within the primary pyrolysis reactor.
 22. A systemfor processing a waste plastic feedstock, the system comprising: aprimary pyrolysis reactor configured to receive a supply of the wasteplastic feedstock, pyrolyze the waste plastic feedstock, and output aprimary hydrocarbon gas stream and a primary solids residue stream; aprimary quenching apparatus configured to receive the primaryhydrocarbon gas stream output from the primary pyrolysis reactor andcondense out a tars product, and to discharge a primary alteredhydrocarbon gas stream; a secondary pyrolysis reactor configured toreceive the tars product, pyrolyze the tars product, and output asecondary hydrocarbon gas stream and a secondary solids residue stream;a secondary quenching apparatus configured to receive the secondaryhydrocarbon gas stream output from the secondary pyrolysis reactor andcondense out a supplemental hydrocarbon product, and to discharge asupplemental altered hydrocarbon gas stream; and at least one condenserconfigured to receive the primary altered hydrocarbon gas stream and thesupplemental altered hydrocarbon gas stream from the primary andsecondary quenching apparatuses and condense out a hydrocarbon oilproduct.
 23. The system of claim 22 wherein a recycling line is arrangedto route the supplemental hydrocarbon product from the secondaryquenching apparatus to the secondary pyrolysis reactor for furtherprocessing.
 24. The system of claim 22, further comprising: a mixing,heating and compacting apparatus configured to receive the supply of thewaste plastic feedstock prior to the primary pyrolysis reactor and tooutput a densified melt of plastic material for supply to the primarypyrolysis reactor.
 25. The system of claim 24 wherein the supply of thewaste plastic feedstock includes halide compounds or heteroatoms fromone or more sources of contamination, and wherein the system furthercomprises: an amendment feed device for providing at least one amendmentselected from the group consisting of alkaline earth oxides, alkalineearth hydroxides, oxides of iron, and oxides of aluminum to be mixed,heated and compacted with the waste plastic based feedstock in themixing, heating and compacting apparatus for subsequent introductioninto the primary pyrolysis reactor.
 26. The system of claim 25 wherein,during the pyrolysis within the primary pyrolysis reactor, the amendmentin the waste plastic feedstock chemically interacts with the halidecompounds or heteroatoms of the waste plastic based feedstock to removeat least a substantial portion of the halide compounds or heteroatomsfrom the primary hydrocarbon gas stream.
 27. The system of claim 22,wherein the supply of the waste plastic feedstock includes halidecompounds or heteroatoms from one or more sources of contamination, andwherein the method further comprises: an amendment feed arrangement forproviding at least one amendment selected from the group consisting ofalkaline earth oxides, alkaline earth hydroxides, oxides of iron, andoxides of aluminum to be combined with the waste plastic feedstock forpyrolysis treatment within the primary pyrolysis reactor.